Conductive compositions and methods of using them

ABSTRACT

A conductive composition includes a mono-acid hybrid that includes an unprotected, single reactive group. The mono-acid hybrid may include substantially non-reactive groups elsewhere such that the mono-acid hybrid is functional as a chain terminator. Methods and devices using the compositions are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 12/567,523 filed on Sep. 25, 2009, now U.S. Pat. No. 8,564,140,which in turn claims priority under 35 U.S.C. §119(e) to U.S.Provisional Patent Application Ser. No. 61/100,525, entitled “CONDUCTIVECOMPOSITIONS AND METHODS OF USING THEM” filed on Sep. 26, 2008, which ishereby incorporated herein by reference in its entirety for allpurposes.

TECHNOLOGICAL FIELD

Certain embodiments disclosed herein relate generally to conductivecompositions. More particularly, certain examples described herein aredirected to compositions produced using mono-acid hybrids that include asingle reactive site.

BACKGROUND

Compositions used to provide an electrical connection can suffer fromoutgassing, premature curing and other unwanted side effects that canreduce the overall usability of such compounds. In particular, prematurecross-linking of the compositions can greatly reduce pot life, whichplaces unwanted time constraints on using the compositions.

SUMMARY

Certain features, aspect, embodiments and examples described herein aredirected to conductive lead free polymer/metal compositions with roomtemperature stability, sufficient enough to render the product useful inhigh volume manufacturing environments for at least about eight hours,for example. More specifically, embodiments disclosed herein may be usedto provide a metal-polymer-composite joint that is formed, afterprocessing the conductive composition, having sufficient thermal and/orelectrical conductivity and exhibiting low contact resistance to replacesoft solder wire, or solder paste in electronic assemblies. Furthermore,the joint can maintain sufficient mechanical strength to reduce or toprevent damage to wire bonds or adversely affect the assembly where itcan not perform its intended function. In certain embodiments, the fluxpower provided by a mono-acid hybrid is sufficient to clean oxide frommetal powders allowing the soldering of metal particles such as, forexample, copper particles, together during a heating profile. Further,the flux can react to eliminate or reduce possible corrosion problemsnormally caused by acidic residues.

In a first aspect, a conductive composition comprising an mono-acidester hybrid comprising an unprotected, single reactive group at a firstterminus and substantially non-reactive groups elsewhere such that theester hybrid is functional as a chain terminator, an epoxy resin, and aneffective amount of at least one metal to render the compositionconductive is provided. In some examples, the composition may alsoinclude an anhydride.

In certain embodiments, the at least one metal is selected from thegroup consisting of copper, silver, tin, bismuth, indium, antimonycoated copper, silver coated copper, tin coated copper and alloysthereof. In other embodiments, the at least one metal is selected fromthe group consisting of capped metal particles, coated metal particles,uncapped metal particles, uncoated metal particles, metal powders, metalflakes, metal alloys and combinations thereof. In some examples, thesingle reactive group of the mono-acid ester hybrid can be a hydroxylgroup. In other examples, the epoxy resin can be selected from the groupconsisting of an epoxidized bisphenol F, an epoxidized bisphenol A, acycloaliphatic epoxy resin, a naphthalenic epoxy resin, an epoxy novalacresin, a dicyclopentadiene epoxy resin, a perfluorinated epoxy resin, anepoxidized silicone resin, a multifunctional epoxy resin andcombinations thereof. In certain examples, the composition may furthercomprise an anhydride selected from the group consisting of methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, nadic methylanhydride and alkenyl succinic anhydride. In additional examples, themono-acid ester hybrid can be present from about 0.5% to about 10% byweight, the epoxidized phenol can be present from about 2% to about 18%by weight, and the metal can be present from about 80% by weight toabout 95% by weight, wherein the weight percentages are all based onweight of the composition.

In certain examples, the metal is silver coated copper, the epoxy resinis epoxidized bisphenol F, and the mono-acid ester hybrid is mono-ethylsuccinate.

In some examples, the metal is present at 80-95% by weight based on theweight of the composition.

In other examples, the mono-acid ester hybrid is a compound having thefollowing formula:

wherein R and R₁ are each independently selected from the groupconsisting of C1-C6 alkyl groups, C1-C6 aliphatic groups, and C1-C9aromatic groups, any of which may be substituted with one or morefunctionalities that are substantially non-reactive to avoidcross-linking with other components of the composition.

In certain examples, the mono-acid ester hybrid is a compound having thefollowing formula:

wherein R₃ is —OH, wherein R₁ is a selected from the group consisting ofa saturated carbon chain including one to six carbon atoms, and whereinn is between one and six to provide an aliphatic or cyclic structurebetween the carbonyl groups.

In another aspect, a conductive composition comprising a metal, a solderor solder alloy, a resin, a mono-acid ester hybrid comprising anunprotected, single reactive group at a first terminus and substantiallynon-reactive groups elsewhere such that the ester hybrid is functionalas a chain terminator is disclosed.

In certain embodiments, the metal can be selected from the groupconsisting of copper, silver, tin, bismuth, indium, antimony coatedcopper, silver coated copper, tin coated copper, alloys thereof andcombinations thereof. In other embodiments, the coating of the metal maybe added using electroless or electrolytic plating. In some embodiments,the metal can be selected from the group consisting of capped metalparticles, coated metal particles, uncapped metal particles, uncoatedmetal particles, metal powders, metal flakes, metal alloys andcombinations thereof. In some examples, the solder comprises tin,bismuth, lead, indium, antimony, and mixtures and alloys thereof andmixtures of alloys.

In certain examples, the resin can be selected from the group consistingof an epoxy resin, a phenolic resin, a phenolic novolac resin, acresolic novalac resin, a polyurethane, a polymide, a maleimide, abismaleimide, a cyanate ester, a dicyanate ester resin, a polyvinylalcohol, a polyester, a polyurea, an acrylic, a polyamide, apolyacrylate, a polysiloxane, a cyanoacrylate and combinations thereof.

In some embodiments, the composition may further comprise at least oneadditional component that comprises one or more reactive moietiesselected from the group consisting of an epoxy group, an amine group, anamide group, an alcohol group, an alkenyl group, an allyl group, anacrylate, a methacrylate, a cyanate ester, a dicyanate ester, amaleimide, a bismaleimide, an anhydride, a benzoxazine and combinationsthereof.

In certain examples, the composition may further comprise an anhydridethat can be selected from the group consisting methyl hexahydrophthalicanhydride, tetrahydrophthalic anhydride, nadic methyl anhydride, alkenylsuccinic anhydride and combinations thereof.

In some examples, the resin may be selected from the group consisting ofepoxidized bisphenol F, epoxidized bisphenol A, a cycloaliphatic epoxyresin, a naphthalenic epoxy resin, an epoxy novalac resin, adicyclopentadiene epoxy resin, a perfluorinated epoxy resin, anepoxidized silicone resin, a multifunctional epoxy resin andcombinations thereof.

In other examples, the single reactive group of the mono-acid esterhybrid is a hydroxyl group. In additional examples, the metal can bepresent from about 80% to about 95% by weight, the solder is presentfrom about 35% to about 65% by weight, the resin is present from about2% by weight to about 18% by weight, the mono-acid ester hybrid ispresent from about 0.5% by weight to about 10% by weight, wherein theweight percentages are all based on weight of the composition.

In certain embodiments, the mono-acid ester hybrid can be a compoundhaving the following formula:

wherein R and R₁ are each independently selected from the groupconsisting of C1-C6 alkyl groups, C1-C6 aliphatic groups, and C1-C9aromatic groups, any of which may be substituted with one or morefunctionalities that are substantially non-reactive to avoidcross-linking with other components of the composition.

In certain embodiments, the mono-acid ester hybrid can be a compoundhaving the following formula:

wherein R₃ is —OH, wherein R₁ is a saturated carbon chain including oneto six carbon atoms, and wherein n is between one and six to provide analiphatic or cyclic structure between the carbonyl groups.

In an additional aspect, a composition comprising a metal and an organicbinder comprising an epoxy resin, and a mono-acid ester hybridcomprising an unprotected, single reactive group at a first terminus andsubstantially non-reactive groups elsewhere such that the ester hybridis functional as a chain terminator is disclosed.

In certain embodiments, the metal can be selected from the groupconsisting of capped metal particles, coated metal particles, uncappedmetal particles, uncoated metal particles, metal powders, metal flakesand metal alloys. In other embodiments, the metal can be selected fromthe group consisting of copper, silver, tin, bismuth, indium, antimonycoated copper, silver coated copper, tin coated copper and alloysthereof.

In certain examples, the mono-acid ester hybrid of the organic binder isa compound having the following formula:

wherein R and R₁ are each independently selected from the groupconsisting of C1-C6 alkyl groups, C1-C6 aliphatic groups, and C1-C9aromatic groups, any of which may be substituted with one or morefunctionalities that are substantially non-reactive to avoidcross-linking with other components of the composition.

In other examples, the mono-acid ester hybrid of the organic binder is acompound having the following formula:

wherein R₃ is —OH, wherein R₁ is a saturated carbon chain including oneto six carbon atoms, and wherein n is between one and six to provide analiphatic or cyclic structure between the carbonyl groups.

In another aspect, an electronic component comprising a semiconductorchip with a solderable surface to provide one or more verticalinterconnection pathways, and a cured electrically conductivecomposition, the composition comprising, prior to curing, an mono-acidester hybrid comprising an unprotected, single reactive group at a firstterminus and substantially non-reactive groups elsewhere such that themono-acid ester hybrid is functional as a chain terminator, an epoxyresin, and an effective amount of at least one metal to render thecomposition electrically conductive is disclosed.

In certain embodiments, the mono-acid ester hybrid of the composition isa compound having the following formula:

wherein R and R₁ are each independently selected from the groupconsisting of C1-C6 alkyl groups, C1-C6 aliphatic groups, and C1-C9aromatic groups, any of which may be substituted with one or morefunctionalities that are substantially non-reactive to avoidcross-linking with other components of the composition.

In certain embodiments, the mono-acid ester hybrid of the composition isa compound having the following formula:

wherein R₃ is —OH, wherein R₁ is a saturated carbon chain including oneto six carbon atoms, and wherein n is between one and six to provide analiphatic or cyclic structure between the carbonyl groups.

In an additional aspect, a semiconductor component comprising asemiconductor chip with a solderable surface to provide one or morevertical interconnection pathways to a substrate, and an electricallyconductive composition comprising at least one of the compositionsdescribed herein is provided.

In another aspect, a method of assembling an electronic componentcomprising a multilayer assembly, the method comprising disposing atleast one of the compositions as described herein on or in a layerbetween a top layer and a bottom layer to provide a thermal and/orelectrical pathway between at least two non-adjacent layers in theelectronic component is disclosed.

In an additional aspect, a method of facilitating assembly of anelectronic component comprising providing a thermally and/orelectrically conductive composition comprising a mono-acid ester hybrid,a resin, an anhydride and an effective amount of a metal to render thecomposition thermally and/or electrically conductive, wherein themono-acid ester hybrid of the composition is a compound having formula(I) or formula (II) as shown herein is provided.

In another aspect, a method of facilitating assembly comprisingproviding at least one of the compositions as described herein isdisclosed.

In an additional aspect, a method of attaching a semiconductor chip to asubstrate comprising depositing a composition as described in the claimson a substrate, depositing an electrical component on the depositedcomposition, and curing the deposited composition to attach thesemiconductor chip to the substrate.

In some examples, any of the compositions described herein may include alatent catalyst. In certain examples, the latent catalyst can beselected from the group consisting of triphenylphosphine (TPP),tetraphenylphosphonium tetraphenylborate (TPP-K), andtriphenylphosphine-benzoquinone (TPP-BQ) and combinations thereof.

In other examples, any of the compositions described herein may includea monofunctional diluent, either alone or with a latent catalyst orother component. In some examples, the monofunctional diluent isselected from the group consisting of a substituted phenyl glycidylether, an alkylphenyl glycidyl ether or an aliphatic glycidyl ether.More specifically, t-butylphenyl glycidyl ether, alkyl C8-C14 glycidylether, butyl glycidyl ether, cresyl glycidyl ether, phenyl glycidylether, nonylphenyl glycidyl ether, 2-ethylhexyl glycidyl ether, andcombinations thereof.

In certain embodiments, the metal used in the compositions describedherein may be capped or coated with one or more materials selected fromthe group consisting of a thermoplastic resin, a solid thermosettingresin, and a self assembly monolayer. In some examples, thethermoplastic resin can be present in an effective amount to increasemechanical properties such as adhesion, fatigue resistance, flexuralstrength, flexural modulus, high temperature modulus, and/or fracturetoughness. In other examples, the metal is coated with an antioxidantmaterial. In certain examples, the antioxidant material is selected fromthe group consisting of a triazole, a benzotriazole, a benzamidizole, animidizole, an organic acid and combinations thereof. In some examples,the antioxidant may be a material that can reduce or prevent oxidationof the metal and can be subsequently removed through a diffusionprocess, dissolution, melting or dissolving.

In an additional aspect, an electronic assembly comprising at least oneelectronic component comprises one or more of the compositions describedherein and an overmold disposed on or around the electronic component isprovided. In some examples, the electronic component is a semiconductorcomponent. In other examples, the overmold can be selected from thegroup consisting of an epoxy mold compound, a silicon encapsulant, aliquid epoxy encapsulant, glass, a transfer molded epoxy resin, and aliquid injected molded resin.

In another aspect, an electronic package comprising an electroniccomponent comprising one or more of the compositions described hereinwithin a cavity package to protect the electronic component isdisclosed. In certain embodiments, the cavity package comprises a lidthat caps the package. In some examples, the lid can be sealed to thecavity package using one or more materials selected from the groupconsisting of solder, glass, frit, and a polymer sealant. In otherexamples, the lid can be sealed to the cavity package using diffusionbonding or aniodic bonding.

In an additional aspect, a method of depositing at least one of thecompositions described herein on a substrate, the method comprisingdispensing the composition on the substrate is provided.

In another aspect, a method of depositing at least one of thecompositions described herein on a substrate, the method comprisingscreen printing the composition on the substrate is disclosed.

In an additional aspect, a method of depositing at least one of thecompositions described herein on a substrate, the method comprisingstencil printing the composition on the substrate is provided.

In another aspect, a method of depositing at least one of thecompositions described herein on a substrate, the method comprisingjetting the composition on the substrate is disclosed.

In an additional aspect, a method comprising applying one or more of thecompositions described herein to a wafer, and drying the wafer. In someexamples, the method may also include polymerizing the appliedcomposition.

In accordance with one or more embodiments, a conductive composition maycomprise at least one metal, a solder or solder alloy, a resin and amono-acid hybrid comprising an unprotected, single reactive group at afirst terminus and substantially non-reactive groups elsewhere such thatthe mono-acid hybrid is functional as a chain terminator.

In some embodiments, the at least one metal is selected from the groupconsisting of copper, silver, silver coated copper, tin coated copper,capped copper, aluminum and combinations thereof. In certainembodiments, the at least one solder or solder alloy is selected fromthe group consisting of bismuth, copper, silver, tin, indium, antimony,alloys thereof and combinations thereof. In at least one embodiment, theat least one metal is selected from the group consisting of capped metalparticles, coated metal particles, uncapped metal particles, uncoatedmetal particles, metal powders, metal flakes, metal alloys andcombinations thereof.

In some embodiments, the mono-acid hybrid is a compound having thefollowing formula:

wherein X equals 1 to 9 and R¹ and R² are each independently selectedfrom the group consisting of H, C1-C6 alkyl groups, C1-C6 aliphaticgroups, C1-C6 alkoxy groups, and C1-C9 aromatic groups, any of which maybe substituted with one or more functionalities that are substantiallynon-reactive to avoid cross-linking with other components of thecomposition.

In some embodiments, the resin is selected from the group consisting ofan epoxidized bisphenol F resin, an epoxidized bisphenol A resin, acycloaliphatic epoxy resin, a aliphatic epoxy resin, a naphthalenicepoxy resin, an epoxy novalac resin, a dicyclopentadiene epoxy resin, aperfluorinated epoxy resin, an epoxidized silicone resin, a biphenylepoxy resin, a hydrogenated bisphenol F resin, a hydrogenated bisphenolA resin, a cyclohexyl diglycidyl ether resin, a multifunctional epoxyresin, a phenolic resin, a phenolic novolac resin, a cresolic novalacresin, a polyurethane, a polymide, a maleimide, a bismaleimide, acyanate ester, a dicyanate ester resin, a benzoxazine, an epoxidizedsilicon, a polyvinyl alcohol, a polyester, a polyurea, an acrylic, anacrylate, a polyolefin, a dicyclopentadiene, a functionalizedpolyurethane, polybutadiene, functionalized polybutadiene,carboxyterminated butadiene-acrylonitrile, a siloxane polyimide, apolyamide, a polyacrylate, a polysiloxane, a cyanoacrylate andcombinations thereof.

In some embodiments, the conductive composition further comprises ananhydride selected from the group consisting of methyl hexahydrophthalicanhydride, tetrahydrophthalic anhydride, nadic methyl anhydride, alkenylsuccinic anhydride and combinations thereof.

In some embodiments, the at least one metal is present from about 10% toabout 60% by weight, the solder is present from about 30% to about 90%by weight, the resin is present from about 1% by weight to about 18% byweight, the mono-acid hybrid is present from about 0.5% by weight toabout 10% by weight, wherein the weight percentages are all based on aweight of the composition. In at least one embodiment, the at least onemetal is copper, the solder or solder alloy is a combination of SnBi andSnAgCu, the epoxy resin is epoxidized bisphenol F, and the mono-acidhybrid is levulinic acid.

In some embodiments, the conductive composition further comprises atleast one additional component that comprises one or more reactivemoieties selected from the group consisting of an epoxy group, an aminegroup, an amide group, an alcohol group, an alkenyl group, a vinylgroup, an acid group, an allyl group, an acrylate, a methacrylate, acyanate ester, a dicyanate ester, a maleimide, a bismaleimide, ananhydride, a benzoxazine and combinations thereof.

In some embodiments, the conductive composition further comprises alatent catalyst selected from the group consisting of triphenylphosphine(TPP), tetraphenylphosphonium tetraphenylborate (TPP-K), andtriphenylphosphine-benzoquinone (TPP-BQ), an imidizole,1-Methylimidazole, 2-Methylimidazole, 2-ethyl-4-methylimidazole,2-ethyl-4methylimidazoline, 2-benzyl-4-methylimidazole,2-benzyl-4-methylimidazoline, 2ethylimidazole, 2-phenylimidazole,2-phenyl-4,5-dihydroxymethyimidazole,1-(2Cyanoethyl)-2-ethyl-4-methylimidazole,1-(2-cyanoethyl)-2-phenyl-4,5-di(cyanoethoxymethyl) Imidazole,1-cyanoethyl-2-methylimidazole, a dicyandiamide,Diamino-6[2′-methylimidazolyl-(1′)]ethyl-striazine 2,4-, isocyanuric,2Heptadecylimidazole and combinations thereof.

In some embodiments, the conductive composition further comprises amonofunctional diluent selected from the group consisting of asubstituted phenyl glycidyl ether, an alkylphenyl glycidyl ether or analiphatic glycidyl ether, in which any of the ethers is one or more oft-butylphenyl glycidyl ether, alkyl C8-C14 glycidyl ether, butylglycidyl ether, cresyl glycidyl ether, phenyl glycidyl ether,nonylphenyl glycidyl ether, 2-ethylhexyl glycidyl ether and combinationsthereof.

In some embodiments, the at least one metal is capped or coated with oneor more materials selected from the group consisting of a thermoplasticresin, a solid thermosetting resin, a self assembly monolayer used as anantioxidant and combinations thereof. In at least one embodiment, theantioxidant material is selected from the group consisting of atriazole, a benzotriazole, a benzamidizole, an imidizole, or an organicacid and combinations thereof.

In accordance with one or more embodiments, an electronic component maycomprise a semiconductor chip with a solderable surface to provide oneor more vertical interconnection pathways, and a cured electricallyconductive composition, the composition comprising, prior to curing, anmono-acid hybrid comprising an unprotected, single reactive group at afirst terminus and substantially non-reactive groups elsewhere such thatthe mono-acid hybrid is functional as a chain terminator, an epoxyresin, and an effective amount of at least one metal to render thecomposition electrically conductive.

In some embodiments, the mono-acid hybrid of the composition is acompound having the following formula:

wherein X equals 1 to 9 and R¹ and R² are each independently selectedfrom the group consisting of H, C1-C6 alkyl groups, C1-C6 aliphaticgroups, C1-C6 alkoxy groups, and C1-C9 aromatic groups, any of which maybe substituted with one or more functionalities that are substantiallynon-reactive to avoid cross-linking with other components of thecomposition.

In accordance with one or more embodiments, a semiconductor componentmay comprise a semiconductor chip with a solderable surface to provideone or more vertical interconnection pathways to a substrate with asolderable surface and an electrically conductive composition comprisingat least one metal, a solder or solder alloy, a resin and a mono-acidhybrid comprising an unprotected, single reactive group at a firstterminus and substantially non-reactive groups elsewhere such that themono-acid hybrid is functional as a chain terminator.

In accordance with one or more embodiments, a method of facilitatingassembly of an electronic component may comprise providing a thermallyand/or electrically conductive composition comprising a mono-acidhybrid, a resin, an anhydride and an effective amount of a metal torender the composition thermally and/or electrically conductive, whereinthe mono-acid hybrid of the composition is a compound having thefollowing formula:

wherein X equals 1 to 9 and R¹ and R² are each independently selectedfrom the group consisting of H, C1-C6 alkyl groups, C1-C6 aliphaticgroups, C1-C6 alkoxy groups, and C1-C9 aromatic groups, any of which maybe substituted with one or more functionalities that are substantiallynon-reactive to avoid cross-linking with other components of thecomposition.

In accordance with one or more embodiments, an electronic assembly maycomprise at least one electronic component comprising a conductivecomposition comprising at least one metal, a solder or solder alloy, aresin and a mono-acid hybrid comprising an unprotected, single reactivegroup at a first terminus and substantially non-reactive groupselsewhere such that the mono-acid hybrid is functional as a chainterminator. The electronic assembly further comprises an overmolddisposed on or around the electronic component, wherein the overmold isselected from the group consisting of an epoxy mold compound, a siliconencapsulant, a liquid epoxy encapsulant, glass, a transfer molded epoxyresin, and a liquid injected molded resin.

In accordance with one or more embodiments, an electronic package maycomprise an electronic component comprising a conductive compositionwithin a cavity package to protect the electronic component. Theconductive composition comprises at least one metal, a solder or solderalloy, a resin and a mono-acid hybrid comprising an unprotected, singlereactive group at a first terminus and substantially non-reactive groupselsewhere such that the mono-acid hybrid is functional as a chainterminator. The cavity package comprises a lid that caps the package andis sealed to the cavity package via diffusion bonding or aniodic bondingusing one or more materials selected from the group consisting ofsolder, glass, frit, and a polymer sealant.

In accordance with one or more embodiments, a method of depositing aconductive composition comprising at least one metal, a solder or solderalloy, a resin and a mono-acid hybrid comprising an unprotected, singlereactive group at a first terminus and substantially non-reactive groupselsewhere such that the mono-acid hybrid is functional as a chainterminator on a substrate is disclosed. The method comprises dispensingthe composition on the substrate, screen printing the composition on thesubstrate, stencil printing the composition on the substrate, jettingthe composition on the substrate, or applying the composition on a waferand drying the wafer.

In accordance with one or more embodiments, a conductive composition maycomprise at least one metal, a solder or solder alloy, a resin and amono-acid ester hybrid comprising an unprotected, single reactive groupat a first terminus and substantially non-reactive groups elsewhere suchthat the ester hybrid is functional as a chain terminator.

In some embodiments, the at least one metal is selected from the groupconsisting of copper, silver, silver coated copper, tin coated copper,capped copper, aluminum and combinations thereof. The at least onesolder or solder alloy may be selected from the group consisting ofbismuth, copper, silver, tin, indium, antimony, alloys thereof andcombinations thereof. In some embodiments, the at least one metal isselected from the group consisting of capped metal particles, coatedmetal particles, uncapped metal particles, uncoated metal particles,metal powders, metal flakes, metal alloys and combinations thereof.

In at least one embodiment, the mono-acid ester hybrid is a compoundhaving the following formula:

wherein R and R₁ are each independently selected from the groupconsisting of C1-C6 alkyl groups, C1-C6 aliphatic groups, and C1-C9aromatic groups, any of which may be substituted with one or morefunctionalities that are substantially non-reactive to avoidcross-linking with other components of the composition.

In some embodiments, the resin is selected from the group consisting ofan epoxidized bisphenol F resin, an epoxidized bisphenol A resin, acycloaliphatic epoxy resin, a aliphatic epoxy resin, a naphthalenicepoxy resin, an epoxy novalac resin, a dicyclopentadiene epoxy resin, aperfluorinated epoxy resin, an epoxidized silicone resin, a biphenylepoxy resin, a hydrogenated bisphenol F resin, a hydrogenated bisphenolA resin, a cyclohexyl diglycidyl ether resin, a multifunctional epoxyresin, a phenolic resin, a phenolic novolac resin, a cresolic novalacresin, a polyurethane, a polymide, a maleimide, a bismaleimide, acyanate ester, a dicyanate ester resin, a benzoxazine, an epoxidizedsilicon, a polyvinyl alcohol, a polyester, a polyurea, an acrylic, anacrylate, a polyolefin, a dicyclopentadiene, a functionalizedpolyurethane, polybutadiene, functionalized polybutadiene,carboxyterminated butadiene-acrylonitrile, a siloxane polyimide, apolyamide, a polyacrylate, a polysiloxane, a cyanoacrylate andcombinations thereof.

In some embodiments, the conductive composition may further comprise ananhydride selected from the group consisting of methyl hexahydrophthalicanhydride, tetrahydrophthalic anhydride, nadic methyl anhydride, alkenylsuccinic anhydride and combinations thereof. In at least one embodiment,the at least one metal is present from about 10% to about 60% by weight,the solder or solder alloy is present from about 30% to about 90% byweight, the resin is present from about 1% by weight to about 18% byweight, and the mono-acid ester hybrid is present from about 0.5% byweight to about 10% by weight, wherein the weight percentages are allbased on a weight of the composition.

In some embodiments, the at least one metal is copper, the solder orsolder alloy is a combination of SnBi and SnAgCu, the epoxy resin isepoxidized bisphenol F, and the mono-acid ester hybrid is mono-ethylsuccinate. The conductive composition may further comprise at least oneadditional component that comprises one or more reactive moietiesselected from the group consisting of an epoxy group, an amine group, anamide group, an alcohol group, an alkenyl group, a vinyl group, an acidgroup, an allyl group, an acrylate, a methacrylate, a cyanate ester, adicyanate ester, a maleimide, a bismaleimide, an anhydride, abenzoxazine and combinations thereof.

In some embodiments, the conductive composition may further comprise alatent catalyst selected from the group consisting of triphenylphosphine(TPP), tetraphenylphosphonium tetraphenylborate (TPP-K), andtriphenylphosphine-benzoquinone (TPP-BQ), an imidizole,1-Methylimidazole, 2-Methylimidazole, 2-ethyl-4-methylimidazole,2-ethyl-4methylimidazoline, 2-benzyl-4-methylimidazole,2-benzyl-4-methylimidazoline, 2ethylimidazole, 2-phenylimidazole,2-phenyl-4,5-dihydroxymethyimidazole,1-(2Cyanoethyl)-2-ethyl-4-methylimidazole,1-(2-cyanoethyl)-2-phenyl-4,5-di(cyanoethoxymethyl) Imidazole,1-cyanoethyl-2-methylimidazole, a dicyandiamide,Diamino-6[2′-methylimidazolyl-(1′)]ethyl-striazine 2,4-, isocyanuric,2Heptadecylimidazole and combinations thereof.

In some embodiments, the conductive composition may further comprise amonofunctional diluent selected from the group consisting of asubstituted phenyl glycidyl ether, an alkylphenyl glycidyl ether or analiphatic glycidyl ether, in which any of the ethers is one or more oft-butylphenyl glycidyl ether, alkyl C8-C14 glycidyl ether, butylglycidyl ether, cresyl glycidyl ether, phenyl glycidyl ether,nonylphenyl glycidyl ether, 2-ethylhexyl glycidyl ether and combinationsthereof.

In at least one embodiment, the at least one metal is capped or coatedwith one or more materials selected from the group consisting of athermoplastic resin, a solid thermosetting resin, a self assemblymonolayer used as an antioxidant and combinations thereof. Theantioxidant material may be selected from the group consisting of atriazole, a benzotriazole, a benzamidizole, an imidizole, or an organicacid and combinations thereof.

In accordance with one or more embodiments, an electronic component maycomprise a semiconductor chip with a solderable surface to provide oneor more vertical interconnection pathways and a cured electricallyconductive composition, the composition comprising, prior to curing, anmono-acid ester hybrid comprising an unprotected, single reactive groupat a first terminus and substantially non-reactive groups elsewhere suchthat the mono-acid ester hybrid is functional as a chain terminator, anepoxy resin, and an effective amount of at least one metal to render thecomposition electrically conductive.

In some embodiments, the mono-acid ester hybrid of the composition is acompound having the following formula:

wherein R and R₁ are each independently selected from the groupconsisting of C1-C6 alkyl groups, C1-C6 aliphatic groups, and C1-C9aromatic groups, any of which may be substituted with one or morefunctionalities that are substantially non-reactive to avoidcross-linking with other components of the composition.

In accordance with one or more embodiments, a semiconductor componentmay comprise a semiconductor chip with a solderable surface to provideone or more vertical interconnection pathways to a substrate with asolderable surface and an electrically conductive composition comprisingat least one metal, a solder or solder alloy, a resin and a mono-acidester hybrid comprising an unprotected, single reactive group at a firstterminus and substantially non-reactive groups elsewhere such that theester hybrid is functional as a chain terminator.

In accordance with one or more embodiments, a method of facilitatingassembly of an electronic component may comprise providing a thermallyand/or electrically conductive composition comprising a mono-acid esterhybrid, a resin, an anhydride and an effective amount of a metal torender the composition thermally and/or electrically conductive, whereinthe mono-acid ester hybrid of the composition is a compound having thefollowing formula:

wherein R and R₁ are each independently selected from the groupconsisting of C1-C6 alkyl groups, C1-C6 aliphatic groups, and C1-C9aromatic groups, any of which may be substituted with one or morefunctionalities that are substantially non-reactive to avoidcross-linking with other components of the composition.

In accordance with one or more embodiments, an electronic assembly maycomprise at least one electronic component comprising a conductivecomposition comprising at least one metal, a solder or solder alloy, aresin and a mono-acid ester hybrid comprising an unprotected, singlereactive group at a first terminus and substantially non-reactive groupselsewhere such that the ester hybrid is functional as a chainterminator. The assembly further comprises an overmold disposed on oraround the electronic component, wherein the overmold is selected fromthe group consisting of an epoxy mold compound, a silicon encapsulant, aliquid epoxy encapsulant, glass, a transfer molded epoxy resin, and aliquid injected molded resin.

In accordance with one or more embodiments, an electronic package maycomprise an electronic component comprising a conductive compositionwithin a cavity package to protect the electronic component. Theconductive composition may comprise at least one metal, a solder orsolder alloy, a resin and a mono-acid ester hybrid comprising anunprotected, single reactive group at a first terminus and substantiallynon-reactive groups elsewhere such that the ester hybrid is functionalas a chain terminator. The cavity package may comprise a lid that capsthe package and is sealed to the cavity package via diffusion bonding oraniodic bonding using one or more materials selected from the groupconsisting of solder, glass, frit, and a polymer sealant.

In accordance with one or more embodiments, a method of depositing aconductive composition comprising at least one metal, a solder or solderalloy, a resin and a mono-acid ester hybrid comprising an unprotected,single reactive group at a first terminus and substantially non-reactivegroups elsewhere such that the ester hybrid is functional as a chainterminator on a substrate is disclosed. The method may comprisedispensing the composition on the substrate, screen printing thecomposition on the substrate, stencil printing the composition on thesubstrate, jetting the composition on the substrate, or applying thecomposition on a wafer and drying the wafer.

Additional aspects, embodiments, examples and features are described inmore detail below.

BRIEF DESCRIPTION OF FIGURES

Certain illustrative embodiments, features and aspects are described inmore detail below with reference to the accompanying figures in which:

FIG. 1 is an IR spectrum of mono-ethylsuccinate, in accordance withcertain examples;

FIG. 2 shows the results of differential scanning calorimetry analysison a composition, in accordance with certain examples;

FIG. 3 is a graph showing the relationship between percent fluxingactivity and millimoles of acid/cubic centimeter, in accordance withcertain examples;

FIG. 4 shows a time profile as a function of temperature for a materialhaving a narrow open time and a fast cure system;

FIG. 5 shows a time profile as a function of temperature for a materialhaving a broad open time and a slow cure system;

FIGS. 6A-6C are representations showing various metal and binderdistributions, in accordance with certain examples;

FIG. 7 is graph showing viscosity change of a formulation, in accordancewith certain examples, where the x axis represents time in hours and they axis represents viscosity in centiPoise; and

FIG. 8 is a differential scanning calorimeter of a formulation duringconversion, in accordance with certain examples.

DETAILED DESCRIPTION

Certain embodiments disclosed herein are directed to conductivecompositions, e.g., thermally conductive, electrically conductive orboth, that include, inter alia, a mono-acid hybrid. As used herein, theterm “mono-acid hybrid,” refers to a hybrid molecule that is used as afluxing agent to remove oxide from metal powder and/or solder powder.The mono-acid hybrid includes an unprotected, single reactive group at afirst terminus, i.e., is monofunctional, and substantially non-reactivegroups elsewhere in the molecule. Due to the monofunctionality of themono-acid hybrid and the non-reactivity of the other groups in themolecule, the hybrid is effective as a chain terminator and not across-linker. In some embodiments, The “free acid” of the mono-acidhybrid can result from the presence of a single carboxylic acidfunctional group, a single sulfonic acid functional group, or a singlephosphonic acid functional group with at least one active proton thatmay be used to remove oxide from metal surfaces. In some examples, themono-acid hybrid acid is saturated (no carbon-carbon double bonds orcarbon-carbon triple bonds but may include keto-groups or othernon-reactive groups having double bonds, for example, aromaticmolecules) to prevent cross-linking through addition reactions (or otherreactions) at the sites of unsaturation. In some non-limitingembodiments, the mono-acid hybrid is a mono-acid ester hybrid

The mono-acid hybrids used in certain examples of the compositionsdisclosed herein differ markedly from those protected acids described inmany existing patents including U.S. Pat. No. 5,376,403 (the '403patent). In the '403 patent, the acids are protected to preventpremature cross-linking of a resin. Cross-linking of the resin canresult in premature cross-linking and increases in viscosity that canreduce the working time of the composition. To avoid prematurecross-linking in the compositions of the '403 patent and in relatedpatents, the cross-linker is chemically protected to reduce thelikelihood of premature cross-linking. Protection of the cross-linkerrequires addition of a protecting group to deactivate the cross-linker.Protection may occur by replacement of the hydrogen of the carboxylicacid group with an alkyl group or other non-reactive functionality.Protected acids require deprotection before the acids can function as across-linker. In addition, the cross-linkers of the '403 patenttypically include more than a single reactive site to function ascross-linkers. In contrast to the cross-linkers of the '403 patent,certain embodiments disclosed herein advantageously utilize a mono-acidhybrid that functions as chain terminator. The use of a mono-acid hybridcan provide significant advantages over the cross-linkers of the '403patent including, but not limited to, fewer steps as no protection ofthe acid is necessary, extended pot-life due to the lack ofcross-linking from the mono-acid hybrid, low viscosity to permit highermetal loadings, reduced likelihood of sublimation, volatization oroutgassing which reduces the overall voiding of the final structure, andthe selection of mono-acid hybrids with high acid values per moleculeweight of the hybrid provides for effective fluxing at low weightlevels.

The compositions disclosed herein may be particularly useful in liquidphase sintering processes and devices produced using liquid phasesintering processes, such as the liquid phase sintering described, forexample, in Shearer et al. “Transient Liquid Phase SinteringComposites.” J. Electronics Mat., 28, 1999, pp. 1319-1326, Palmer et al.“Forming High Temperature Soldering Joints Through Liquid PhaseSintering of Solder Paste.” J. Electronics Mat., 28, 1999, pp.1189-1193, Palmer et al. “Forming Solder Joints by Sintering EutecticTin-Lead Solder Paste.” J. Electronics Mat., 28, 1999, pp. 912-915,German, Randall M. Sintering Theory and Practice. (1996), German, R₁, M.Liquid Phase Sintering. (1985) and German and Messing. SinteringTechnology. 1996.

In certain embodiments, the compositions disclosed herein may furtherinclude a resin, an anhydride, catalysts, curatives and other componentsthat may be desirable to produce a binder for use with a conductivematerial. In addition to being electrically conductive, the binder mayalso function as an adhesive or have adhesive properties. Illustrativecompositions are discussed in more detail below. One or more componentsof the compositions may provide a binder that is effective to removesurface oxide layers from metal surfaces to facilitate good wetting andmetal network formation. In some embodiments, the composition mayinclude one or more of a mono-acid hybrid (which can act as a chainterminator), a latent catalyst (including but not limited to TPP, TPP-K,TPP-BQ), a monofunctional epoxy diluent with low ionic impurities (whichcan act as chain terminators), low mole equivalents of flux (which canreduce metal salt formation), a barrier coating to prevent or reduceoxidation of metal powder and/or prevent reaction of the mono-acidhybrid with the metal

Most of electronic component assembly today is performed using softsolder wire, solder paste or highly silver filled thermosettingadhesives. These technologies are generally referred to as soft solderdie attach or die attach adhesives. Die attach joining technology servestwo general purposes to the end user; (1) is used transfer heat orelectrical current from a semiconductor, discrete or LED chip to thesubstrate or heat sink; (2) provide mechanical attachment of the chip(which may include, for example, Si, GaAs, SiN or other semiconductormaterials) to the substrate, where the attachment allows post processingsuch as wirebonding, additional chips to be stacked, and polymerencapsulation.

Solder wire, is a preferred technology approach for power semiconductor,power discrete and discrete applications due to the relatively highthermal conductivity of tin-lead based solders as well as good wettingto metallic surfaces leading to low contact or interfacial resistance.End users typically select SnPb based alloys due to their high meltingpoint, more specifically they prefer alloys with melting points greaterthan 265° C., which is a common peak reflow temperature of lead freealloys common in board assembly of electronics such as mobile phones andtelevisions. It is desirable to that the die attach material does notmelt and/or flow during the attachment of the component to a printedwiring board or circuit board (this attachment is commonly referred toas board assembly). Metal filled conductive adhesives do not reflowsince the polymer network is cross linked with very limited mobility.However, solder alloys with melting points greater than 265° C., becomeliquid and can flow out of the joint causing shorts and lose mechanicalstrength that may compromise wire bond integrity. Several globalinitiatives have mandated elimination of lead from electronicassemblies, however, high lead solders are currently exempted since, atpresent day, no lead free die attach material exists that provides therequired high thermal conductivity and no flow during lead free boardassembly reflow conditions.

In some examples, the compositions are functional as a flux in that theycan remove surface oxidation from the metal component to provide goodoverall conductivity. For example, the mono-acid hybrid component canremove oxides from metals. Unlike existing acids used in similarcompositions, the hybrids used herein provide compositions that do notsuffer from premature curing that occurs in compositions formed usingacidic cross-linkers. Thus, the hybrid components described herein donot need any protecting groups to prevent cross-linking as no suchcross-linking occurs.

Certain embodiments disclosed herein provide compositions that are roomtemperature stable and/or are suitable to render the product useful inhigh volume manufacturing environments for at least 8 hours. Thecompositions may be used, for example, to clean oxide from metal powdersallowing the soldering of copper particles together during a heatingprofile. Further, the composition may react to reduce or eliminatecorrosion problems commonly encountered by acidic residue.

In certain examples, the composition may include one or more of amono-acid hybrid, a latent catalyst, a monofunctional epoxy diluent, alow mole equivalent of flux, and a barrier coating. As discussed hereinby using a mono-acid hybrid that functions a chain terminator, thepot-life of the composition may be extended. Monofunctional epoxydiluents with low ionic impurities may be used and act in similarfashion as mono-acid hybrids as chain terminators to reducecross-linking and thereby minimizing viscosity increases. A barriercoating may be used in the metals used in the compositions disclosedherein to prevent (1) oxidation of the metal powder, and/or (2)mono-acid hybrids from reacting with Cu or Sn metal. The barrier coatingcan be in form of polymer coating on the metal particle or a metalbarrier coating, that in essence, is less prone to salt formation thatthe metal being coated. It is desirable that the polymer coating doesnot melt or dissolve in the organic media between −40° C. and +40° C.because this temperature range is a desirable storage and usetemperature of the composition. The barrier metal may be selected fromsilver, gold, platinum, palladium, tin, nickel, indium or alloys thereofas a coating over the metal. In one embodiment, the metal may be copperor other metal that is susceptible to oxidation. Metal salts, morespecifically copper salts, can catalyze the polymerization of epoxyresins which lead to high viscosity liquids and ultimately gelation.There are two implications of this uncontrolled polymerization: (1)viscosity increases at room temperature lead to thick or unusableproduct that does not easily dispense or spread; this viscosity increasemost likely results in poor wetting of the composition which leads topoor adhesion, soldering and electrical and thermal transfer; and/or (2)dissolved metal salts influence rate of cure of the composition. It ispreferred that the polymerization be controlled below the gel point ofthe polymer composition thereby allowing the molten solder to movefreely and connecting copper particles together. In effect, if thepolymer system builds molecular weight too quickly, and gels or hardens,then the molten solder can be immobilized and copper particles willremain discrete and no solder connection is made. This lack ofconnection results in poor thermal and electrical conductivities.

In accordance with one or more embodiments, a mono-acid hybrid maycomprise an unprotected, single reactive group at a first terminus andsubstantially non-reactive groups elsewhere such that the mono-acidhybrid is functional as a chain terminator. In some embodiments, themono-acid hybrid is a compound having the following generic formula (I)representative of mono-acid hybrids suitable for use in the compositionsdisclosed herein.

wherein X equals 1 to 9 and R¹ and R² are each independently selectedfrom the group consisting of H, C1-C6 alkyl groups, C1-C6 aliphaticgroups, C1-C6 alkoxy groups, and C1-C9 aromatic groups, any of which maybe substituted with one or more functionalities that are substantiallynon-reactive to avoid cross-linking with other components of thecomposition. In certain examples, the CHR² group between the twocarbonyl groups may take the form of a cyclic ring such as, for example,cyclobutane, cyclopentane or cyclohexane. In such instances, two of theCHR² groups would instead be CH groups to provide the propertetra-valency for the ring carbons. In some examples, R¹ may be selectedfrom methyl, ethyl, propyl and other saturated alkyl chains, forexample, aliphatic or branched alkyl chains, having between one and sixcarbon atoms. The groups selected for R¹ may be substituted with one ormore heteroatom containing groups including, but not limited to,tertiary amines or other groups including a heteroatom and beingsubstantially non-reactive. The mono-acid hybrid of formula (I) may beselected such that the carboxyl group of formula (I) is generally theonly reactive site in the molecule. Thus, no substantial cross-linkingoccurs using the molecule of formula (I) but instead, formula (I)functions as a chain terminating agent that controls the MW of thepolymer. The mono-acid hybrid can function as a fluxing agent to removeoxide from metal powder and/or solder powder. In particular, the protonof the carboxyl group may provide active protons used to remove theoxide from metal surfaces. The mono-acid hybrids are monofunctional andoperative as chain terminators to extend the overall pot life of thecompositions. A composition that includes an unprotected liquidmultifunctional carboxylic acid (i.e. capable of cross linking), adifunctional epoxy, an anhydride, a copper powder, and a solder powderrapidly increases in viscosity and becomes too thick to mix after 60minutes. The same formulation with the mono-acid hybrid results in noviscosity increase (or very minimal). Using standard titrationtechniques with a base indicator indicates the mono-acid hybrid providesacid values. In at least one embodiment, the mono-acid hybrid isLevulinic acid. The Levulinic acid may have an acid value of about 460mg KOH/gram.

In accordance with one or more embodiments, the mono-acid hybrid may bea mono-acid ester hybrid. In some embodiments, the mono-acid esterhybrid comprises a single, unprotected carboxyl group that can functionas a free acid to donate protons. Generic formula (II) is representativeof mono-acid ester hybrids suitable for use in the compositionsdisclosed herein.

In formula (II), the mono-acid ester hybrid include a single free acidgroup (—COOH) and an ester group connected to each other through an Rgroup. The mono-acid ester hybrids are unprotected throughout thereaction, which reduces the numbers of steps used to provide thecompositions and simplifies production of the compositions. Themono-acid ester hybrid can function as a fluxing agent to remove oxidefrom metal powder and/or solder powder. In particular, the proton of thecarboxyl group may provide active protons used to remove the oxide frommetal surfaces. The mono-acid ester hybrids are monofunctional andoperative as chain terminators to extend the overall pot life of thecompositions. By way of example, when a mono-acid ester hybrid is addedto a copper powder, a blue-green color results within about an hourwhich indicates fluxing action at room temperature. A composition thatincludes an unprotected liquid multifunctional carboxylic acid (i.e.capable of cross linking), a difunctional epoxy, an anhydride, a copperpowder, and a solder powder rapidly increases in viscosity and becomestoo thick to mix after 60 minutes. The same formulation with themono-acid ester hybrid results in no viscosity increase (or veryminimal). Using standard titration techniques with a base indicatorindicates the mono-acid ester hybrid provides acid values.

In certain embodiments, the compositions disclosed herein may include amono-acid ester hybrid that includes a carboxyl group, an ester group,and a selected number of atoms between them. A generic formula of onemono-acid ester hybrid is shown below as formula (III)

In formula (III), n may vary and is typically one to twelve, moreparticularly, one to nine, for example, one to six or one to three. Incertain examples, the CH₂ group between the two carbonyl groups may takethe form of a cyclic ring such as, for example, cyclobutane,cyclopentane or cyclohexane. In such instances, two of the CH₂ groupswould instead be CH groups to provide the proper tetra-valency for thering carbons. In some examples, R₁ may be selected from methyl, ethyl,propyl and other saturated alkyl chains, for example, aliphatic orbranched alkyl chains, having between one and six carbon atoms. Thegroups selected for R₁ may be substituted with one or more heteroatomcontaining groups including, but not limited to, tertiary amines orother groups including a heteroatom and being substantiallynon-reactive. The mono-acid ester hybrid of formula (III) may beselected such that the carboxyl group of formula (III) is generally theonly reactive site in the molecule. Thus, no substantial cross-linkingoccurs using the molecule of formula (III) but instead, formula (III)functions as a chain terminating agent. The use of such chainterminating agents provides unexpected advantages and results, ascompared to compositions using cross-linking agents, including, but notlimited to, lower viscosities, less likelihood of premature curing,permission of higher conductive material loading rates due to a moreopen network, less void formation due to decreased carbon dioxideevolution and the like.

In certain embodiments, the mono-acid ester hybrid may be produced byreacting an anhydride with an excess of an alcohol. In certain examples,the alcohol that is reacted with the anhydride may be methanol, ethanol,propanol, isopropanol, butanol, sec-butyl alcohol, t-butyl alcohol orother alcohols having one to six carbon atoms. In some examples, thealcohol is a saturated alcohol. The alcohol is typically an alcoholcomprising a single OH group and not a diol or polyol. The exactanhydride that is reacted with the alcohol may vary, and in someexamples, the anhydride is one or more of succinic anhydride,2,2-dimethylglutaric anhydride, 2,2-dimethylsuccinic anhydride, ethanoicanhydride, propanoic anhydride, butanoic anhydride, pentanoic anhydride,hexanoic anhydride, heptanoic anhydride, octanoic anhydride, nonanoicanhydride, decanoic anhydride, dodecanoic anhydride,methylhexahydrophthalic anhydride (MHHPA) or other suitable aliphatic orcyclic saturated anhydrides. The exact number of atoms in the anhydridemay be selected to vary the overall network of the compositions. Forexample, it may be desirable to react the alcohol with an anhydridehaving more carbon atoms to provide a less densely packed binder,whereas in other examples, an anhydride having fewer carbon atoms may beused to provide a binder with closer packing.

In a particular embodiment, a mono-acid ester hybrid may be produced byreaction of succinic anhydride with excess ethanol as shown in thereaction scheme below.

The mono-acid product may be produced, for example, using heterogeneousand homogeneous catalysis as described, for example, by Nandhini et al.,J. Mol. Cat. A: Chem, vol. 243, 2006, pp. 183-193, and Bart et al., Int.J. Chem. Kin, vol. 26, 1994, pp. 1013-1021. However, catalysis is notrequired. In particular, large quantities of mono-ethyl succinate may beproduced through the elevated temperature alcoholysis of succinicanhydride without the use of catalysis, using an excess of ethanol asshown in the reaction scheme above. The excess ethanol may besubsequently removed from the reaction mixture under reduced pressure.

In some embodiments, amide esters (or other nucleophilic groups) may beused with, or in place of, the mono-acid ester hybrid, as shown informula (IV) below.

In formula (IV), R₃ may be —NH₂, —SH, —OH or other suitable nucleophilicgroups or leaving groups depending on the desired reaction of themolecule. R₁ may be any of those groups discussed above in reference toformulae (II) or (III), and n may vary and is typically one to twelve,more particularly, one to nine, for example, one to six or one to three.

In certain examples, the compositions disclosed herein may also includea reactive monomer or polymer which, in some examples, may take the formof an anhydride that may be combined with the mono-acid hybrid and/orthe metal. In some examples, the anhydride may be selected from(2-dodecen-1-yl)succinic anhydride, (2-nonen-1-yl)succinic anhydride,1,8-naphthalic anhydride, methyl hexahydrophthalic anhydride,tetrahydrophthalic anhydride, nadic methyl anhydride, alkenyl succinicanhydride, 2,3-dimethylmaleic anhydride, 3-hydroxyphthalic anhydride,4-methylphthalic anhydride, dimethylmaleic anhydride, diphenylmaleicanhydride, or other suitable anhydrides. Because of its rigid bicyclicstructure, nadic methyl anhydride yield polymers with higher glasstransition temperatures. Alkenyl succinic anhydrides impart lowermoisture absorption and a lower glass transition temperature to thepolymer because of their long aliphatic chain. The exact number of atomsin the anhydride may be selected to vary the overall network of thecompositions. For example, it may be desirable to use anhydrides havingmore carbon atoms to have a more open polymer network with more voidvolume, whereas in other examples, an anhydride having fewer carbonatoms may be used to provide a binder with closer packing. In someexamples, the anhydride may include about three to about twelve carbonatoms, more particularly about four to about eight carbon atoms, forexample about five to about seven carbon atoms. Similarly, the degree ofunsaturation in the anhydride may be selected to promote cross-linkingor deter cross-linking, with higher degrees of unsaturation favoringincreased levels of cross-linking.

In certain embodiments, the compositions disclosed herein may includeone or more metals. The exact form of the metal added to the compositionmay vary and in certain examples the metal may be a powder, for example,a sintered or unsintered powder, a salt, particles, nanoparticles, forexample capped or uncapped nanoparticles, flakes, for example with alubricant, or other forms that metals may take such as those described,for example, in WO2008017062. As used herein, capped metal particlesrefer to those that include an organic moiety functionalized to themetal group, whereas coated metal particles refer to those where one ormore other materials has been deposited in some manner on the metal butthere is not necessarily any chemical bond between the metal and thedeposited material. In certain examples, the metal may take the form ofsilver coated copper, tin coated copper or antimony coated copper. Bycoating the copper with silver or another protective material, surfaceoxidation of the copper may be greatly reduced and overall conductivitymay be improved. Thus, in some embodiments, the metal may be coated withan antioxidant material such as, for example, those materials commonlyused to reduce, resist or inhibit oxidation, e.g., polymer coatings. Inother examples, metal may be capped or coated with a thermoplasticresin, a solid thermosetting resin, or a self assembly monolayer.Illustrative examples of suitable thermoplastic resins include, but arenot limited to, polyimides (PI), siloxane polyimides (SPI), polysulfone(PS), polyphenyl sulfone, polyethersulfones (PES, PESU), polyaryleneethers (PAE), phenoxy resins, polyetheretherketone (PEEK) polyesters(PE), polytetrafluoroethylene (PTFE), Polyamides (PA), polyoxymethylene(POM), polybutylene terephthalate (PBT), liquid crystal polymers (LCP),crosslinked silicones, and polyurethanes (PU). Illustrative examples ofsuitable solid thermosetting resins include, but are not limited to,epoxy resins, phenolic epoxy resins, cresol novalic epoxy resins,cycloaliphatic epoxy resins, naphthalenic epoxy resins,dicyclopentadiene epoxy resins, biphenyl epoxy resins, epoxidizedsilicon resins, maleimide resins, bismaleimide resins, cyanate esterresins, dicyanate ester resins, benxozazine resins, acrylate resins,methacrylate resins, polyolefin resins, functionalize polyurethanes,polybutadiene resins, functionalized polybutadiene resins,carboxy-terminated butadiene-acrylonitrile (CTBN). Illustrative examplesof materials that can form self assembling monolayers include, but arenot limited to, a triazole, a benzotriazole, a benzamidizole, animidizole, or an organic acid. In some examples, a majority of theweight of the compositions is from the metal. For example, the weightpercent of the metal, based on the weight of the composition, may begreater than 50%, greater than 75% or even greater than 90% or 95% suchthat the overall composition is highly electrically conductive.

In certain embodiments, the exact metal used may vary and includes, butis not limited to, silver coated copper, copper, silver, aluminum, gold,platinum, palladium, rhodium, nickel, cobalt, iron, molybdenum andalloys and mixtures thereof. In embodiments where the metal is provided,at least in part, by including a solder in the composition, the soldermay include, but is not limited to, tin, bismuth, lead, zinc, gallium,indium, tellurium, mercury, thallium, antimony, selenium and mixturesand alloys thereof. In some examples, a first metal and a second metalmay be used. In certain examples, the melting points of the two metalsmay differ with the amount of each metal selected to provide a desiredconductivity and/or desired physical properties to the overallcomposition.

In certain examples, the metal used in the compositions disclosed hereinmay be provided in more than one form. For example, metal powder may bemixed with a metal alloy solder to provide different types of metals inthe composition. Thus, the source or type of metal in the compositionsmay be different and may vary. For example, the metals in thecomposition may be, for example, silver coated copper in combinationwith a tin-bismuth or a SnAgCu solder alloy.

In certain embodiments, the compositions disclosed herein may alsoinclude a resin such as, for example, an epoxy resin. Illustrative epoxyresins include, but are not limited to, low viscosity liquid epoxies ofparticular interest include epoxidized bisphenol F, epoxidized bisphenolA, cycloaliphatic epoxies, naphthalenic epoxy Epiclon® HP-4032D (DIC,Japan), and multifunctional epoxy MY-0510 (Huntsman, USA). The bisphenolA and F resins are low viscosity, thus allowing for higher metalloadings, and yield polymers with low-to-moderate glass transitiontemperatures (T_(g)'s). Naphthalenic epoxy HP-4032D gives a higher T_(g)and is reportedly more hydrolysis resistant, but its viscosity is alsoconsiderably higher. Cycloaliphatic and multifunctional epoxy MY-0510can potentially provide both low viscosity and T_(g)'s.

In some examples, the compositions disclosed herein may also include oneor more carboxylic acids. In certain examples, a carboxylic acid havingthe following properties may be selected: 1) low viscosity and 2) lowequivalent weight (high acid values). This presents a challenge, in thatmost of the low-molecular weight aromatic monocarboxylic acids (benzoic,phenyl acetic acid etc.,) and the aliphatic dicarboxylic acids typicallyused in flux formulations (glutaric, succinic and adipic acid) arecrystalline solids with melting points less than or equal to 80° C. Whenused in the compositions disclosed herein, these materials can act toincrease the viscosity.

In certain embodiments, a stoichiometric mixture of epoxidized bisphenolF resin, with MHHPA and a generic carboxylic acid may be used in thecompositions disclosed herein. An illustrative combination of thesematerials and an illustrative product is shown below.

Illustrative weight percentages for the components used in thecompositions disclosed herein are discussed in more detail below.

In certain embodiments, the compositions disclosed herein may be used ina liquid phase sintering (LPS) process to provide materials suitable foruse in preparing electrical devices and/or joints between components inan electrical device. In liquid phase sintering, the liquid phase existsfor a short period as a result of the homogenization of the metals inthe composition. For example two or more different metals may beselected which exhibit a eutectic point or melt at some composition andat some temperature T₁. A mixture of the two metals may be prepared inthe proportion of the desired final, the final composition being a solidat T₁. Heating of the mixture to T₁ results in the formation of a liquidphase. The liquid phase has a very high solubility in the surroundingsolid phase, thus diffusing rapidly into the solid and eventuallysolidifying at temperature T₁. Diffusional homogenization provides afinal composition without the need to heat the mixture above itsequilibrium melting point. LPS may be used in the compositions disclosedherein to provide a material that includes a metal and a binder system.The material may be used in forming electrical joints, conductive pathsor other suitable structures in electrical devices including, but notlimited to, printed circuit boards. In some examples, the viscosity ofthe material may be selected such that printed circuits may be providedby depositing a desired pattern on a substrate and then sintering and/orcuring the deposited pattern. During heating, the binder material isoperative as a flux for the metal(s), which permits the liquid phasesintering process to occur. After heating, the binder can bind anyresulting oxides.

In certain examples, one or more solvents, catalyst, additives, diluentsand the like may be used with or in preparing of the compositionsdescribed herein. The exact solvent or solvents selected may depend, atleast in part, on the desired viscosity of the mixture and the desiredsolubility of the components in the solvent. Suitable solvents include,but are not limited to, ketones, acetates, esters, lactones, alcohols,ethers, polyethers, glycol ethers, glycol ether esters, hydrocarbons,aromatic solvents, alkylaryl ethers and terpenes. More specifically,acetone, methyl ethyl ketone, cyclohexanone, ethanol, propanol, butanol,butyl ether, dibasic esters, 4-butyrolactone, carbitol acetate, butylcarbitol acetate, and propylene glycol monomethyl ether acetate (PMacetate). Additional suitable solvents will be readily selected by theperson of ordinary skill in the art, given the benefit of thisdisclosure and based on the particular materials selected for use in thecomposition. Illustrative latent catalysts such as, for example, TPP,TPP-K, TPP-BQ are described herein. Exemplary monofunctional diluentsinclude, but are not limited to, those described herein.

In certain embodiments where the composition includes a mono-acidhybrid, an epoxy resin, an anhydride and at least one metal, the weightpercentages of the components, based on the weight of the compositionmay vary as follows: about 0.5% to about 10% by weight mono-acid hybrid,about 2% to about 10% by weight epoxy resin, about 0.5% to about 8% byweight anhydride, and about 80% to about 95% by weight metal. Inembodiments where the composition includes a metal, a solder, a resin, amono-acid hybrid, and an anhydride, the weight percentages of thecomponents, based on the weight of the composition may vary as follows:about 80% to about 95% by weight metal, about 35% to about 65% by weightsolder, about 2% to about 10% by weight resin, about 0.5% to about 10%by weight mono-acid hybrid, and about 0.5% to about 8% by weightanhydride. In embodiments where the composition includes a metal and anorganic binder, the weight percentages of the components, based on theweight percent of the composition may be about 80% to about 95% byweight metal and 5% to about 20% by weight binder. Where the binderitself includes an epoxy resin, an anhydride, and an mono-acid hybrid,the weight percentages of the components in the binder, based on theweight of the binder, may vary as follows: about 20% to about 90% byweight resin, about 0% to about 45% by weight anhydride, and about 5% toabout 40% by weight mono-acid hybrid. Additional weight percentages maybe used depending on the desired properties of the material.

In certain embodiments, the compositions disclosed herein may includeadditional components, additives, curatives, catalysts and the like. Insome examples, at least one additional component or material thatinclude one or more reactive moieties selected from an epoxy group, anamine group, an amide group, an alcohol group, an alkenyl group, anallyl group, an acrylate, a methacrylate, a cyanate ester and amaleimide may be used in the compositions disclosed herein. Catalystssuch as imidazole, phosphines, phosphates, amide, phenols, metal saltsincluding, but not limited to, metal carboxylates or acetoacetenoatemetal complexes such as, for example organo-tin complexes and the likemay be used. Initiators such as peroxides may be also added. Viscositymodifiers may be included in some examples.

In certain examples, the compositions disclosed herein may be used inelectronic components where thermal and/or electrical conductivity maybe desired between the semiconductor chip and a substrate or heat sink.For example, the compositions may be used to provide a thermal and/or anelectrical path between a semiconductor chip and a substrate or heatsink. In some examples, a device comprising at least three layerswherein at least one of the layers comprises one or ore of thecompositions disclosed herein is provided. For example, the device mayinclude a bottom layer, an interconnect layer comprising the conductivecomposition and a top layer. One or more thermal and/or an electricalconnections may be provided between the top and bottom layers throughthe interconnect layer that includes one or more of the compositionsdisclosed herein. For example, the top may include one or moresemiconductor chips or other electrical devices that may be produced,for example, by semiconductor wafer fabrication techniques on, forexample, a Si, GaAs, or SiC wafer. The bottom layer may be comprised offlexible or rigid, polymer, composite, ceramic or a metal substrate orother suitable materials. In some layers, a composition as disclosedherein that has been deposited and cured into a simple or complexpattern onto a suitable substrate provides adhesion between the bottomlayer and the top layer and may also provide the thermal and electricalinterconnection between the bottom of the chip that is coated with asolderable metal to the metal lead frame or substrate. In some examples,the compositions may be used to provide specialized connections such asdie attach solder or adhesive or the like.

In other examples, the compositions disclosed herein may be used toprovide a thermal connection between a flip chip die mounted on anorganic or ceramic substrate with one or more areas or layers to a metalheat sink. For example, an interconnect produced using one or more ofthe compositions disclosed herein may provide a thermal path between asurface mounted die and a metal heat sink. In other examples, one ormore of the compositions disclosed herein may be deposited on a top ofthe flip chip die that has a solderable surface, followed by placementof a lid on the deposited material, and after curing, a thermalconnection may be provided between the die and the top layer or metalheat sink.

The adhesive characteristics of the compositions disclosed herein mayalso be used to retain the die to a desired surface. For example, anelectronic component may be produced that includes an attached die,where the assembly includes a via interconnect layer which has one ormore of the electrically conductive compositions disclosed hereinpatterned into suitable dielectric materials. In some examples, thesuitable dielectric materials provide adhesion between the substrate anda component or die while the electrically conductive compositionsprovide the electrical interconnection and adhesion between connectingpads of substrate and the attached semiconductor chip.

In certain embodiments, a method of assembling an electronic componentcomprising disposing a middle layer comprising at least one of thecompositions disclosed herein on a bottom layer and disposing a toplayer on the middle layer is provided. The overall assembly may befurther processed, for example, subjected to curing, sintering, a reflowor rework operation or the like, or additional components including, butnot limited to, dies may be attached to the top layer or the bottomlayer. Additional layers or material may be deposited to provide amulti-layer printed circuit board.

In an illustrative method, an electronic component with at least onevertical interconnect, produced using one or more of the compositionsdisclosed herein, may include a single chip or multiple chips, on thesame planar surface, or attached vertically. One or more of thecompositions disclosed herein may then be applied by a variety oftechniques, such as dispensing, stencil printing, screen printing,jetting, stamping, doctor blading, curtain coating, or, again, by othermethods known to those skilled in the art, onto each of these substratesin a desired pattern, each layer being the same or different from otherlayers. The compositions may then be cured, or simply dried and leftuncured while the thin substrates are aligned and bonded together underpressure. The bonding pressure can force the conductive layers tointerconnect the substrates, interconnection being made wherever theaforementioned conductive composition within the contacts circuit padsof the same adhesive composition on either side. Curing of thecomposition may be done before, during or after this bonding process.The result is a multi-layered electronic component.

When the compositions disclosed herein are used in preparing printedcircuit boards, the cure temperature may range from about 220° C. toabout 290° C., more particularly about 255° C. to about 285° C., forexample, about 265° C. to about 275° C. Suitable dielectric materialsfor use include, but are not limited to, polyimides, copper cladpolyimides, and similar materials.

In certain examples, the compositions disclosed herein may be used in amethod of assembling an electronic component comprising a multilayerassembly. In certain examples, the method may comprise disposing one ormore of the compositions disclosed herein in a layer between a top layerand a bottom layer to provide a thermal and/or electrical pathwaybetween at least two non-adjacent layers in the electronic component.

In some examples, a method of facilitating assembly of an electroniccomponent is provided. In certain examples, the method comprisesproviding one or more of the compositions disclosed herein optionallywith instructions for using the composition. In some examples, a kitincluding a composition and instructions for using it may also beprovided.

In certain examples, a composition that has been cured is provided. Insome examples, the composition may include any one or more of thecompositions described herein for example, a cured form of a compositioncomprising a mono-acid hybrid that is functional as a chain terminator,an epoxy resin, an anhydride, and an effective amount of at least onemetal to render the composition electrically conductive. In otherexamples, the cured composition may be a cured form of a compositioncomprising a metal, a solder or solder alloy, a resin, a mono-acidhybrid that is functional as a chain terminator, and an anhydride. Inyet other examples, the cured composition may be a cured form of acomposition a metal, and an organic binder comprising an epoxy resin, ananhydride, and a mono-acid hybrid that is functional as a chainterminator. In some non-limiting embodiments, the mono-acid hybrid maybe a mono-acid ester hybrid.

In certain embodiments, the compositions disclosed herein may be used ona wafer level. For example, pre-applying one or more of the compositionsto a wafer or substrate followed by drying or partial polymerization(b-staging) may be performed. The composition may include, for example,a solid thermosetting resin that can provide a tack free surface afterdrying or b-staging. In addition, the b-staging could be controlled byselecting resin types that have different cure kinetics. The intent isto cure (i.e., cross-link) only a portion of the organic binder suchthat it yields a tack free surface that allows the end user easyhandling. The unreacted or latent resin is soft and can provide anadhesive bond with the aid or heat, pressure or both. The compositionmay alternatively, or in addition, include a solid mono-acid hybridmolecule, for example, a solid mono-acid ester hybrid molecule, to aidin creating a tack-free composition on the wafer or substrate. Once thecomposition is deposited on the wafer or substrate, it may be storedunder ambient conditions. It may be desirable for the metal powders tobe coated or encapsulated by a noble metal that does not easily oxidizeor an organic or polymer coated metal particle such that the organic orpolymer coating, melts, vaporizes, dissolves and dissociates allowingsolder to metal bonding. It is also desirable that the composition hassufficient mechanical properties after drying or b-staging such that thewafer or substrate can be easily diced or singulated without chippingthe composition or gumming the dicing blade. The composition may alsocontain thermoplastic resin that provides sufficient mechanical strengthduring the wafer level process.

In certain embodiments, the compositions disclosed herein may be used inor with an electronic assembly comprising at least one electroniccomponent that includes an overmold disposed on or around the electroniccomponent. In some examples, the electronic component is a semiconductorcomponent. In other examples, the overmold can be selected from thegroup consisting of an epoxy mold compound, a silicon encapsulant, aliquid epoxy encapsulant, glass, a transfer molded epoxy resin, and aliquid injected molded resin or other suitable compounds that canprovide protection from heat, the environment or other conditions in ause environment.

In certain examples, an electronic package comprising an electroniccomponent comprising one or more of the compositions described hereinwithin a cavity package to protect the electronic component isdisclosed. In certain embodiments, the cavity package may include a lidthat caps the package. In some examples, the lid can be sealed to thecavity package using one or more materials selected from the groupconsisting of solder, glass, frit, and a polymer sealant. In otherexamples, the lid can be sealed to the cavity package using diffusionbonding, aniodic bonding or other processes to attach or bond the lid tothe package.

In certain embodiments, a method of depositing at least one of thecompositions described herein on a substrate comprising dispensing thecomposition, screen printing the composition, stencil printing thecomposition, jetting the composition, or the like, on the substrate isdisclosed. The printing or depositing may be performed manually or usingautomated printing devices. The viscosity of the composition may beadjusted using a viscosity modifier or diluent to facilitate theselected mode of deposition.

In some embodiments, a method comprising applying one or more of thecompositions described herein to a wafer is provided. In some examples,the wafer may be dried and/or the composition may be polymerized.Additional steps including, but not limited to, further processing ofthe wafer may also be performed. For example, a semiconductor component(or other electronic component), including wire bonds and interconnectsmay be further protected by encapsulation using a transfer molded epoxyresin, liquid injected molded resin, a liquid encapsulant, a siliconencapsulant or other suitable materials. The semiconductor may also befurther protected by packing in a closed environment of a lidded cavitypackage, as described herein.

Certain specific examples are described below to further illustrate someof the novel features of the technology described herein.

Example 1

A mono-acid ester hybrid was prepared by reacting an excess of ethanolwith succinic anhydride at a temperature of 165° C. followed by vacuumevaporation of any residual ethanol. An IR spectrum (smear on a KBrplate) of the resulting mono-ethyl succinate is shown in FIG. 1. Inaddition to an acidic —OH stretch at about 3350 cm⁻¹, the material ischaracterized by both a ester-carbonyl (1735 cm⁻¹) and a acid-carboxylstretch (1714 cm⁻¹).

Example 2

A composition was prepared that included 88% by weight of metal andusing the mono-acid ester hybrid from Example 1. When normalized for themetals content, the mixture consisted of copper powder (30-60%), SACalloy (0-35%), SnBi (0-35%) and silver flake (0-10%).

The organic binder/flux system consisted primarily of epoxidizedbisphenol F as the epoxy (50-60%), MHHPA (24-30%) as the anhydride andmono-ethyl succinate (14-22%) as the acid. Using a standard imidazolecatalyst, the ratio of epoxy to hardener (anhydride+acid) was maintainedat stoichiometric balance (1:1), but the acid/anhydride molar ratio wasvaried from 0.2 to 0.8. After blending, the mixtures were analyzed in adifferential scanning calorimeter using a multi-step dynamic profile(heat-cool-heat) from 25-300° C., 20° C./min ramp rate. The ratio of themelt enthalpy of the SnBi solder (T_(melt)˜145° C.) during the 2^(nd)heat cycle, divided by the melt enthalpy during the 1^(st) heat cycle,was used as a quantitative measure of solder alloy conversion and hencefluxing activity (Equation 1 and FIG. 2).

$\begin{matrix}{{\%\mspace{14mu}{conversation}} = {100 \cdot ( {1 - \lbrack \frac{\Delta\; H_{2}}{\Delta\; H_{1}} \rbrack} )}} & (1)\end{matrix}$The measured composition included 88% metal content (35.2% SnBi, 52.8%Cu), and 60 mol-% acid in the hardener. The initial melt enthalpy of thepure SnBi alloy was about 57 J/g, which, at a 32.5% loading would giveΔH=19 J/g. The observed ΔH value of 15.5 J/g is lower due to a partialsuperposition of the polymerization exotherm. The percent conversion iscalculated as 100*(1−[2.4/19.0])≈87%. The peak appearing at ˜208° C. inthe 2^(nd) heating cycle is attributed to formation of a new,high-melting metal alloy.

Starting from the known equivalent weights of epoxy (162 g/mol),anhydride (168 g/mol) and mono-acid ester hybrid (146 g/mol), assumingan average density of 1.0 g/cm³ for the organic phase (12% by weight)and an average density of the metals of approximately 9.0 g/cm³ (88% byweight), it is useful to convert from mole-% acid in the organichardener portion to moles-acid/cm³ in the fully-formulated LPS. With 88%metal loading, the approximate density of the LPS is:

$= {\frac{1}{( \frac{0.12}{1.0} ) + ( \frac{0.88}{9.0} )} = {4.59\mspace{14mu} g\text{/}{cm}^{3}}}$Within this unit volume, there is 0.12×4.59 g of organic binder≈0.55 g.In the case of 40 mol-% mono-ethyl succinate acid in the hardener, theweight (and volume) fraction of mono-acid ester hybrid in the organicportion is:

$= {\frac{0.4 \cdot 146}{{0.4 \cdot 146} + {0.6 \cdot 168} + {1.0 \cdot 162}} = 0.182}$The amount of acid per unit volume is therefore 0.182×0.55 g=0.10 g or0.10 g/146 g mol⁻¹=0.687 mmol/cm³. For 100 mol-% acid as the hardener,the amount of acid rises to 1.79 mmol/cm³. From the DSC experiments, thegeneral trend in % conversion vs. acid is shown in FIG. 3.

Example 3 Cure Kinetics and Reflow Profile

Controlling the cure kinetics of the polymer phase is desirable for theoptimal performance of the materials. The “open-time” in these systemsmay be characterized by the time between when solder melting occurs, andthe time when the polymer gels—which essentially freezes-in themorphology at that instant. See J. Hurley et al. Proc., 52^(nd) Elect.Comp. Tech Conf. 2002. pp: 828-833. FIG. 4 shows a material having anarrow open time and a fast cure system, and FIG. 5 shows a materialhaving a broad open time and a slow cure system.

On the one hand, the binder must not gel so quickly, as to inhibit thefluxing reaction and formation of a continuous metal network above thesolder liquidus. On the other hand, the two networks (metal and polymer)are thermodynamically incompatible due to differences in their densitiesand surface energies. Over an extended open-time at temperature abovethe liquidus, gross phase separation of the metal and polymer phaseswill occur—leading to a morphology with less than desirable properties.This relationship is shown diagrammatically in FIGS. 6A-6C, where themetal (gray) and the polymer (yellow) are shown as a function of time.Referring to FIG. 6A, insufficient open time leads to poor networkformation with isolated metal particles. A moderate open time leads todesirable network formation with conductive pathways (FIG. 6B).Excessive open time may lead to gross phase separation of the metal andpolymer domains and poor electrical properties (FIG. 6C). Variation inthe open time may be achieved by changing the type and concentration ofcure accelerator used, and by varying the reflow profile.Characterization of the cure kinetics using experimental DSC data andkinetic models such as the “autocatalytic” or Kamal-Sourour approach arehighly useful in this regard. See Y. Lei et al. J. Appl. Poly. Sci, vol.100, (2006) pp. 1642-1658.

Example 4

A composition may be prepared that includes a mono-acid ester hybrid, aresin capable of reaction with the hybrid, a metal power (e.g., copperpowder) and a solder. The ester hybrid may include a carboxylic acid andmay contain organic groups to enhance mechanical properties or improvecompatibility with the organic phase. Optionally the copper is protectedwith a barrier coating. Optionally a latent catalyst is added to controlcure kinetics and gelation. Optionally a monofunctional reactive diluentis added to control molecule weight.

Example 5

A monofunctional sulfonic acid and a resin capable of reaction with thesulfonic acid, a copper powder, and a solder may be used to prepare acomposition. The sulfonic acid molecule may contain organic groups toenhance mechanical properties or improve compatibility with the organicphase. Optionally the copper is protected with a barrier coating.Optionally a latent catalyst is added to control cure kinetics andgelation. Optionally a monofunctional reactive diluent is added tocontrol molecule weight.

Example 6

A monofunctional phosphonic acid, a resin capable of reaction with thephosphonic acid, a copper powder, and a solder may be used to prepare acomposition. The phosphonic acid molecule may contain organic groups toenhance mechanical properties or improve compatibility with the organicphase. Optionally the copper is protected with a barrier coating.Optionally a latent catalyst is added to control cure kinetics andgelation. Optionally a monofunctional reactive diluent is added tocontrol molecule weight

Example 7

A monofunctional perfluoro carboxylic acids, a resin capable of reactionwith the perfluoro carboxylic acid, a copper powder, and a solder may beused to prepare a composition. The perfluoro carboxylic acid moleculemay contain organic groups to enhance mechanical properties or improvecompatibility with the organic phase. Optionally the copper is protectedwith a barrier coating. Optionally a latent catalyst is added to controlcure kinetics and gelation. Optionally a monofunctional reactive diluentis added to control molecule weight

Example 8

A composition that contains a molecule with one acid functional groupcapable of removing metal oxide and a separate functional group capableof polymerization in which proton exchange is not involved in thereaction pathway may be used to prepare a composition as describedherein.

Example 9

A composition that contains a molecule with one acid functional groupcapable of removing metal oxide and a thermoplastic resin withappropriate functional groups capable of binding and tight associationwith the acid functional group such that it is immobilized to preventcorrosion may be used to prepare a composition as described herein.

Example 10

Any of the compositions disclosed herein may include a UV curable resincapable of reacting with the molecule capable of fluxing. The UV curableresin can be cured after the metal network is formed in order toimmobilize the flux residue.

Example 11

A composition such that the cure kinetics and the molecular weight aredesigned to minimize polymer domain size within the compositionstructure leading to a joint where a polymer domain is less than 50% ofthe bond line thickness may be prepared. This thickness can becontrolled by reactivity and functionality of the reactive polymericresin, the amount of mono-acid ester hybrid molecule, the type andamount of catalyst, the heating profile, and/or the type and amount ofmonofunctional reactive resin.

Example 12

Preapplying one or more of the compositions to a wafer or substratefollowed by drying or partial polymerization (b-staging) may beperformed. One suitable composition may include a solid epoxy resin thatwould result in tack free surfaced after drying or b-staging. Inaddition, the b-staging could be controlled by selecting resin typesthat have different cure kinetics. The intent is to cure (i.e.,cross-link) only a portion of the organic binder such that it yields atack free surface that allows the end user to handle with ease. Theunreacted or latent resin is soft, or is capable of softening whenheated, and forms and adhesive bond during with the aid or heat,pressure or both.

Example 13

The mono-acid ester hybrid may be used in a cleaning process to removeoxide from the metal powders prior to mixing with the organic phase andto limit the monofunctional carboxylic acid used to provide for goodsintering. This composition may also contain stabilizers to preventoxidation of the metal powder during storage and handling

Example 14

Any of the compositions disclosed herein may be used in combination witha “proton sponge” such as, for example, 1,5-dialkyl pyridines toregulate acid levels in the composition.

Example 15

Several paste formulations were made by mixing various levels of copperpowder with solder powders, epoxy resin, mono ester acid ester hybrid,anhydride and catalyst. Formulations listed in Table 1 were prepared byfirst mixing the organic components and then slowly adding metal powderswith mixing. The formulations resulted in a smooth lump free creamypaste. All formulations were prepared with 8% organic binder and 92%metal filler. The ratios of the organic components were kept constantfor formulations A, B and C. A ten gram sample, referenced as Run A intable 1 was prepared by mixing 3.7 grams of a low oxygen containingcopper powder (mean particle size ˜25 microns), 2.76 grams ofSn(42)Bi(58) solder powder, 2.76 grams of SnAgCu solder powder, with0.13 grams of the mono acid ester hybrid listed in Example 1, 0.43 gramsof electronic grade epoxidized bisphenol F resin, 0.01 g of 2P4MZimidazole catalyst, and 0.23 g of a liquid anhydride.

Bulk thermal conductivity samples were prepared for formulations A, Band C. The samples were prepared by dispensing the paste in a siliconemold and reflowed using the temperature profile specified in FIG. 4.Bulk thermal conductivities were obtained by using a Netzsch LFA 447tester. The results are listed in Table 1. The values in the table belowrefer to the ratios of Cu, SnBi and SAC, based on the amounts of thesethree components in the mixture, and not the weight percentages orabsolute values in the overall composition.

TABLE 1 Run Cu SnBi SAC K_(Bulk), W/m-K A 40 30 30 30 B 45 27.5 27.5 26C 50 25 25 29.2

Example 16

Several paste formulations were made by mixing various ratios of SnAgCuand SnBi solder powders with copper powders, epoxy resin, mono esteracid ester, anhydride and catalyst. Formulations listed in Table 2 wereprepared by first mixing organic components then slowly adding metalpowders with mixing. The formulations resulted in a smooth lump freecreamy paste. All formulations were prepared with 8% organic binder and92% metal filler. The ratios of the organic components were keptconstant for formulations D through G. A ten gram sample, referenced asRun D in Table 2 was prepared by mixing 3.7 grams of a low oxygencontaining copper powder (mean particle size ˜25 microns), 1.84 grams ofSn(42)Bi(58) solder powder, 3.68 grams of SnAgCu (SAC) solder powder,with 0.13 grams of the mono acid ester hybrid listed in example 1, 0.43grams of electronic grade epoxidized bisphenol F resin, 0.01 g of 2P4MZimidazole catalyst, and 0.23 g of a liquid anhydride. The values in thetable below refer to the relative ratios of Cu, SnBi and SAC and not theweight percentages or absolute values.

TABLE 2 Run Cu SnBi SAC K_(Bulk), W/m-K D 40 20 40 24.2 E 40 40 20 36.6F 45 27.5 27.5 32 G 45 27.5 27.5 27.4 H 50 20 30 25.2 I 50 30 20 32.7

Example 17

Several reflow conditions including time above liquidus, peaktemperature and post bake conditions were evaluated and listed in Table3. Formulation B from Example 15 was used for all conditions listed inTable 3. The shape of the reflow curve was generally consistent with thecurve shown in FIG. 2 however peak temperatures and time above 230° C.was varied.

TABLE 3 Time Above Post-bake 230° C. Peak Temp at 175 C. K_(effective,)(sec) (° C.) for X HRS W/m-K 30 245 Yes, 1 hr 16 30 245 Yes, 4 hrs 12180 245 None 25 30 265 None 24 30 265 Yes, 1 hr 23 30 265 Yes, 4 hrs 13180 265 None 31 180 265 Yes, 1 hr 47 180 265 Yes, 4 hrs 38

Example 18

Several paste formulations were made by mixing various types of epoxycatalysts with SnAgCu solder powder, SnBi solder powders, a silvercoated copper powder, epoxy resin, mono ester acid ester, anhydride andcatalyst. Formulations listed in Table 4 were prepared by first mixingorganic components then slowly adding metal powders with mixing. Theformulations resulted in a smooth lump free creamy paste. Allformulations were prepared with 8% organic binder and 92% metal filler.The ratios of the organic components were kept constant for formulationsD through G. A ten gram sample, referenced as Run J-K in Table 4 wereprepared by mixing 4.1 grams of a silver coated copper powder (meanparticle size ˜25 microns), 2.53 grams of Sn(42)Bi(58) solder powder,2.53 grams of SnAgCu solder powder, with 0.13 grams of the mono acidester hybrid listed in example 1, 0.43 grams of electronic gradeepoxidized bisphenol F resin, 0.01 g of either catalyst listed in Table4, and 0.23 g of a liquid anhydride.

TABLE 4 K_(effective,) Run Catalyst K_(Bulk), W/m-K W/m-K J 2P4MZ 23.121.1 K TPPK 22.6 18.8 L 2E4MZ 20 22

Example 19

Two formulations with various levels of monofunctional acid esters withSnAgCu solder powder, SnBi solder powder, a silver coated copper powder,epoxy resin, anhydride and catalyst were made. Formulations listed inTable 5 were prepared by first mixing organic components then slowlyadding metal powders with mixing. The formulations resulted in a smoothlump free creamy paste. All formulations were prepared with 8% organicbinder and 92% metal filler. A ten gram sample, referenced as Run M, inTable 4 was prepared by mixing 3.7 grams of a low oxygen containing Cupowder (mean particle size ˜25 microns), 2.76 grams of Sn(42)Bi(58)solder powder, 2.76 grams of SnAgCu solder powder, with 0.13 grams ofthe mono acid ester hybrid listed in example 1, 0.43 grams of electronicgrade epoxidized bisphenol F resin, 0.01 g of 2P4MZ imidazole catalyst,and 0.23 g of a liquid anhydride. A ten gram sample, referenced as RunN, in Table 4 was prepared by mixing 3.7 grams of a low oxygencontaining Cu powder (mean particle size ˜25 microns), 2.76 grams ofSn(42)Bi(58) solder powder, 2.76 grams of SnAgCu solder powder, with0.16 grams of the mono acid ester hybrid listed in example 1, 0.43 gramsof electronic grade epoxidized bisphenol F resin, 0.01 g of 2P4MZimidazole catalyst, and 0.2 g of a liquid anhydride.

TABLE 5 K_(effective,) Run Flux Conc. K_(Bulk), W/m-K W/m-K M 0.4 38.522 N 0.6 34 17

Example 20 Work Life

It is common in the electronic assembly and semiconductor packagingindustry to test the “pot life” or “work life” of a paste composition bymeasuring increase of viscosity vs. time at ambient conditions. It isgenerally accepted that a viscosity increase of <100% over an eight hourperiod is workable on a manufacturing line. FIG. 7 shows the viscositychange for Formulation B from Example 15. The test was carried out usinga Brookfield DVII+ with a CP-51 spindle. Values are listed incentipoises at 5 RPM rotation.

Example 21 Conversion Compared to Other Acids

The monofunctional acid ester hybrid from Example 15 has been found tohave superior fluxing power compared with more conventional liquid acidssuch as dimmer acid or a solid acid such as succinic acid. Severalformulations were prepared to show superior fluxing efficacy of themono-functional acid ester hybrid resins with equivalent moleequivalents of acid. For example, A 10 gram sample, with 0.02 moleequivalents (0.277 grams) of the mono acid ester hybrid listed inexample 1, mixed with 5.95 grams of a low oxygen containing Cu powder(mean particle size ˜25 microns), 1.28 grams of Indium solder powder,1.28 grams of SnAgCu solder powder, 0.9 grams of electronic gradeepoxidized bisphenol F resin, 0.002 g of 2P4MZ imidazole catalyst, and0.32 g of a liquid anhydride. The disappearance of In and SnAgCu alloyswas monitored by Differential Scanning calorimetry (DSC) as it wasconverted to corresponding copper intermetallics. This conversion islisted on the Y axis of FIG. 8. Formulations using succinic acid ordimer acid were made replacing the mono acid ester hybrid and balancingthe formulations with correct mole equivalents of epoxidized bisphenol Fresin and anhydride. Conversion of In to corresponding copperintermetallics was measured as shown in FIG. 8

Example 22 Demonstration of Free Mono Acids, for Example, Levulinic Acid

Several paste formulations were made to test different terminatingacids. SnAgCu powder with copper powder were combined with epoxy resins,a keto acid (levulinic acid) or mono-ethyl succinate, and a catalyst.Formulations listed in Table 6 were prepared by first mixing organiccomponents then slowly adding metal powders with mixing. Theformulations resulted in a smooth lump free creamy paste. Bothformulations were prepared with 12% organic binder and 88% metal filler.A ten gram sample, referenced as Run 1 in Table 6, was prepared bymixing 2.2 grams of a low oxygen containing copper powder (mean particlesize ˜25 microns), 6.6 grams of low oxygen SnAgCu (SAC) solder powder,with 0.2 grams of the levulinic acid, 0.4 grams of electronic gradeepoxidized 1,6 hexanedioldiglycidyl resin, 0.3 grams MHHPA, 0.2 grams ofa monofunctional aliphatic glycidyl ether, 0.01 g of TPPK catalyst, and0.23 g of a liquid anhydride. The results in Table 6 represent theeffectiveness of the chain terminating mechanism from use of eitherLevulinic Acid or Mono-ethyl Succinate, which both provide long potlifewhile achieving excellent bulk thermal conductivity.

TABLE 6 Potlife- Run Flux Acid Organic Cu SnBi SAC hrs K_(Bulk)m-K 1Levulinic 12 26.4 0 61.6 >15 25.0 Acid 2 Mono-ethyl 12 26.4 0 61.6 >1527.4 Succinate

When introducing elements of the examples disclosed herein, the articles“a,” “an,” and “the” are intended to mean that there are one or more ofthe elements. The terms “comprising,” “including” and “having” areintended to be open ended and mean that there may be additional elementsother than the listed elements. It will be recognized by the person ofordinary skill in the art, given the benefit of this disclosure, thatvarious components of the examples can be interchanged or substitutedwith various components in other examples.

Although certain features, aspects, examples and embodiments have beendescribed above, additions, substitutions, modifications, andalterations of the disclosed illustrative features, aspects, examplesand embodiments will be readily recognized by the person of ordinaryskill in the art, given the benefit of this disclosure.

What is claimed is:
 1. An electronic component, comprising: asemiconductor chip with a solderable surface to provide one or morevertical interconnection pathways; and a cured electrically conductivecomposition disposed on the solderable surface of the semiconductorchip, the composition comprising, prior to curing, an mono-acid hybridcomprising an unprotected, single reactive group at a first terminus andsubstantially non-reactive groups elsewhere such that the mono-acidhybrid is functional as a chain terminator, an epoxy resin, and aneffective amount of at least one metal to render the compositionelectrically conductive, wherein the mono-acid hybrid of the compositionis a compound having the following formula:

wherein X equals 1 to 9 and R¹ and R² are each independently selectedfrom the group consisting of H, C1-C6 alkyl groups, C1-C6 aliphaticgroups, C1-C6 alkoxy groups, and C1-C9 aromatic groups, any of which maybe substituted with one or more functionalities that are substantiallynon-reactive to avoid cross-linking with other components of thecomposition.